This disclosure relates to a generator rotor and its rotor circuit.
A generator includes a stator fixed relative to a housing and a rotor rotatable about an axis relative to the stator. The rotor includes a rotor frame carrying a rotator circuit that includes field turns and a rectifier assembly, which has diodes. Rotation of the rotor relative to the stator induces an alternating current in the field turns, which is converted to a DC voltage by the rectifier assembly.
Generators can experience rectifier assembly failures due to damaged diodes. One failure mode results from an electrical static discharge event from the rotor frame to the isolated rotor circuit. Typically, the rotor frame has an opening through which a bus bar extends. The bus bar, which is electrically connected to the rotor circuit, is electrically insulated from the rotor frame with an insulator bushing. The isolated rotor circuit builds up a high voltage potential to the rotor frame under some operational parameters. The parasitic capacitances within the isolated rotor circuit discharges to the rotor frame. The voltage across the diodes in the rotor circuit exceeds the diode voltage rating during the discharge event. The reverse bias on the diode breaks down and shorts when the voltage exceeds the avalanche voltage characteristic of the silicone die, thus damaging the rectifier assembly.